1. Field of the Invention
The present invention relates to drive devices for optically recording information onto or reproducing recorded information from an information layer of an optical information recording medium (hereinafter referred to as an optical disc).
2. Description of the Background Art
As conventional drive devices, devices for recording information onto or reproducing information from optical discs such as Compact Discs (CDs), Digital Versatile Discs (DVDs), and Blu-ray Discs (Registered Trademark; BDs) have been developed and manufactured.
Japanese Laid-Open Patent Publication No. 2001-222827 (Patent Literature 1), for example, discloses the above drive devices. Such drive devices disclosed in Patent Literature 1 are provided with an optical pickup which employs an astigmatism method. Such drive devices operate as follows in order to suppress crosstalk caused by crossing tracks on an optical disc. The drive device stores in memory the relations of the phase and the amplitude between a push-pull signal of a main spot and a cycle component of focus crosstalk crossing toward the outer diameter side. Using a push-pull signal of a half track pitch distanced sub spot or main spot, the drive device invokes data representing the stored relations of the phase and the amplitude, and thereby produces a focus crosstalk signal. Then, through a calculation using the focus crosstalk signal and a focus signal of the main spot, the drive device offsets the track crossing crosstalk.
However, the drive devices disclosed in Patent Literature 1 require, at the time of start-up, a large amount of time to generate a signal (data representing the relations of the phase and the amplitude) for correcting the crosstalk.
More specifically, the drive devices disclosed in Patent Literature 1 rotate an optical disc at the time of start-up so as to detect a focus error signal, and thereby perform focus control and tracking control. Since the drive devices need to read and learn a push-pull signal and a focus crosstalk signal, the drive devices require a large amount of time to generate a signal (relation data) for correcting crosstalk.